The IEEE 802.11 communications protocol allows a client to roam among multiple access points that may be operating on the same or separate channels. IEEE 802.11 communications are generally effected through wireless LAN access points (APs), which are typically single standalone units, but can include networks with multiple APs which provide a roaming function. To support the roaming function, each access point typically transmits a beacon signal every 100 ms. A roaming station (STA) uses the beacon to gauge the strength of its existing access point connection. If the STA senses a weak signal, the roaming STA can implement the reassociation service to connect to an access point emitting a stronger signal.
IEEE 802.11 supports two power modes; active and power-saving (PS). The protocols for infrastructure networks and ad hoc networks are different. Under an infrastructure network, there is an AP to monitor the mode of each mobile station. A station in the active mode is fully powered and thus may transmit and receive at any time. On the contrary, a station in the PS mode only wakes up periodically to check for possible incoming packets from the AP. A station always notifies its AP when changing modes. Periodically, the AP transmits beacon frames spaced by a fixed beacon interval. A PS station should monitor these frames. In each beacon frame, a traffic indication map (TIM) are delivered, which contains IDs of those PS stations with buffered unicast packets in the AP. A PS station, on hearing its ID, should stay awake for the remaining beacon interval. Under the contention period (i.e., DCF), an awake PS station can issue a PS-POLL to the AP to retrieve the buffered packets. While under the contention-free period (i.e., PCF), a PS station waits for the AP to poll it. The AP sends delivery TIMs (DTIMs) within beacon frames to indicate that there are buffered broadcast packets. The delivery TIMs are spaced by a fixed number of beacon intervals. Immediately after DTIMs, the buffered broadcast packets are sent.
Since IEEE 802.11 presumes that mobile stations are fully connected, the transmission of a beacon frame can be used to synchronize all stations' beacon intervals. In addition to the use in IEEE 802.11, beacon signals are useful in other WLAN communications and wireless communications in general. Periodic measurements are performed in systems implementing the third generation partnership program (3GPP) wideband code division multiple access (W-CDMA) system. Such systems use a time division duplex mode. To support higher layer functions in IEEE 802.11 standards for efficient network management, several physical parameters relating to different aspects of network management are desirable.
One such parameter is the perceived signal to noise indicator (PSNI), the measurement of which provides a quantized, comparative measure of received signal quality for all channels/rates and among all physical channels and between all stations. Another parameter is the received channel power indicator (RCPI) indicator, which is a measure of the received RF power in the selected channel, measured at the antenna connector. The RCPI parameter may be a measure by the PHY sub layer of the received RF power in the channel measured over the PLCP preamble and over the entire received frame. RCPI is a monotonically increasing, logarithmic function of the received power level defined in dBm. The exemplary allowed values for the RCPI parameter may be an 8-bit value in the range from 0 through 220.
In known approaches, the measurement of the parameters RCPI and PSNI is done as a single measurement, which approach has certain disadvantages. It is desirable to provide an improved method of making measurements of the parameters, e.g., RCPI and PSNI, to result in specific advantages resulting in more efficient network management.